<span>E. Stimulation of T-cell by APC</span>
The initial exposure of the body to an infectious agent e.g. through a vaccine, triggers an immune response most of which rapidly diminishes after the vaccination. However some cells of the immune system called lymphocytes remain with a memory of that pathogen.As a result, if the same pathogen infects a vaccinated person, the memory cells remember and recognize it and rapidly spring into action triggering a much more rapid response specific to that pathogen than the initial exposure, effectively dealing and neutralizing the pathogen.
Answer:
Some amino acids are encoded by more than one codon, inasmuch as there are 64 possible base triplets and only 20 amino acids. In fact, 61 of the 64 possible triplets specify particular amino acids and 3 triplets (called stop codons) designate the termination of translation.
(1) they keep toxic substances out of the cell;
(2) they contain receptors and channels that allow specific molecules, such as ions, nutrients, wastes, and metabolic products, that mediate cellular and extracellular activities to pass between organelles and between the cell and the outside environment;
(3) they separate vital but incompatible metabolic processes conducted within organelles.
The correct answer to this question would be "B", co-dominance.
Answer:
mRNA: Carry genetic information from DNA to protein; serve as template for protein synthesis.
tRNA: Serves as adapter molecule and deliver specific amino acid from the cell pool to the mRNA-ribosome complex.
rRNA: Structural component of ribosomes.
Explanation:
There are three types of nongenetic RNAs: mRNA, tRNA, and rRNA.
1. The messenger RNA (mRNA) is formed by the process of transcription in the nucleus. Transcription uses template strand of DNA to specify the nucleotide sequence in mRNA. The mRNA enters cytoplasm to join ribosomes. The nucleotide sequence of mRNA serves as a template and specifies the amino acid sequence of proteins.
2. The transfer RNA (tRNA) serves as an adapter molecule during the process of protein synthesis and binds to the specific amino acids to deliver them to the protein-synthesizing machinery. The anticodon of tRNA binds to the complementary mRNA codons.
3. The ribosomal RNA (rRNA) serves as structural components for ribosomes. Each of the subunits of ribosomes is made up of rRNA and proteins.